Variable Focus Lens Package

ABSTRACT

Proposed is a variable focus lens package ( 2 ) including lens ( 31, 75 ) as covers, which covers are provided as moulded replica layers ( 31, 75 ) on a substrate ( 30, 74 ) and are provided with integral alignment means ( 33, 77 ).

The invention relates to a variable focus lens package comprising aplurality of optical elements in a light path, which plurality ofoptical elements comprises:

a fluid optical element in a fluid chamber comprising a first fluid anda second fluid, which are non-miscible, and which are in contact over ameniscus, wherein a shape of the meniscus is variable under theapplication of a voltage to an electrically conducting surface of thefluid chamber, said fluid chamber being surrounded by an encapsulation;

a non-fluid optical component that is part of the encapsulation of thefluid chamber,

of which fluid optical element and which non-fluid optical element atleast one is a lens.

The invention also relates to a method of manufacturing such a variablefocus lens package.

Such a variable focus lens package is for instance known from WO-A2003/0693080. The known lens package comprises a fluid lens of theelectrowetting type and a first and a second conventional non-fluidlenses at opposite sides of the fluid lens. The first fluid is anelectrically insulating fluid and the second fluid is an electricallyconducting fluid, but could alternatively be a polar fluid. The firstlens is a convex-convex lens of highly refracting plastic, and having apositive power. At least one of the surfaces of the first lens isaspherical, to provide desired initial focusing characteristics. Thesecond lens is formed of a low dispersive plastic, and includes anaspherical lens surface which acts as a field flattener. The first lensis formed as a single body with a cylindrical tube that forms part ofthe encapsulation of the fluid chamber. The second lens may extendbeyond the encapsulation of the fluid chamber.

It is a disadvantage of the lens package, that its assembly to furtherlenses and/or its integration with an image sensor is difficult. Thisassembly needs to be carried out with a holder that holds the lenspackage and any further lenses at any side faces. Nonetheless,electrical connections need to be provided at least one of the sidefaces in order to supply the voltage to the fluid lens. Moreover, theone or more lenses and the image sensor need to be aligned properly inorder to have a proper optical quality.

It is therefore a first object of the invention to provide an variablefocus package of the kind mentioned in the opening paragraph, that canbe assembled more easily. It is a second object of the invention toprovide a method of the kind mentioned in the opening paragraphs thatreduces the amount of tolerance in the manufacture and hence improvesthe lens quality.

The first object is achieved in that the non-fluid optical component isconstructed from a substrate that comprises a transparent portion in thelight path, and from a moulded surface layer that is present at a sideof the substrate facing away from the fluid optical element and furthercomprises alignment means for alignment of the lens package with furtherlenses.

The second object is achieved in that in a plurality of such packagesare made simultaneously with the steps of (1) assembling a carriercomprising a plurality of cavities filled with at least one of saidfluids to a substrate with transparent portions for each of the lightpaths, which substrate has a moulded surface layer that includes thenon-fluid lens and alignment means for alignment with further lenses,and (2) separating said plurality of lenses into individual variablefocus lenses.

The moulded surface layer of the invention allows the integration oflens functionality and alignment features. The integration of alignmentfeatures in the moulded surface layer allow that they are defined in themould. Hence, they are defined in a standardized manner, which isindependent of the position of side faces. Therewith, the alignment—atleast with other optical components—is made independent of the actualseparation process.

The alignment features are here present at the bottom and/or top side ofthe lens package. It is therewith possible to make a stack of lenses ina desired manner. As a consequence of the proper alignment, it will beeasier than in the prior art device to make such a stack. Therewith, thevariable focus lens can be held relatively simple and standardized. Atthe same time, the stacking of various lenses to arrive at a zoom lensis helped. The use of a moulding process furthermore allows that thealignment features are defined with any desired and specified height.The height of the alignment feature can be different from that of thelens. This height definition allows a positioning of the lens not onlylaterally, but also a positioning at a specified distance to otherlenses.

It is preferred with respect to the alignment features, that they aredefined at both sides of the lens, or as a ring-shaped feature. Thisreduces the risk of undesired optical effects as a consequence of “outof plane” assembly. In such out of plane assembly there is an anglebetween the lens axes that is unequal to zero degrees.

Moreover, the assembly can be carried out with plates instead of withindividual lenses having non-planar surfaces. This reduces the amount ofassembly, and it will minimize tolerances in the alignment within thelens. Another advantageous feature of the invention is the reduction ofthe total height of the package.

Lenses that are defined with moulding techniques are known per se, suchas from the U.S. Pat. Nos. 4,615,847 and 4,890,905. However, thesepatents disclose the manufacture of standard lenses only. In theinvention, the moulding technique is used to provide both lensfunctionality and alignment functionality, which has furthermore thebenefit of providing a standardized mechanical interface of theelectrowetting lens. Moreover, since the electrowetting lens comprises asingle meniscus, there is no need to provide a non-fluid lens with twocurved surfaces. One moulded surface layer on a substrate is thusprincipally sufficient.

Furthermore, the non-fluid optical component is particularly a lens, ora lens surface. Alternatively, however, it may be a diaphragm, a gratingor the like. A preferred lens shape is aspherical to provide desiredinitial focussing characteristics. The replica technique applied in theinvention allows the provision of structures up to some millimetresthickness, of which very strong lenses can be made.

The non-fluid optical component obtained with the replica technique maycontain dyes or other chemical compound. This leads to a system withadditional functionality. The dye is for instance a photochromiccompound, such as that obtainable as MXP7-114 from PPG Industries. Thetransparency of the optical component is dependent on the lightintensity. If the light intensity is very high, the transparency will berelatively low. As a consequence, the intensity of the light arriving atthe image sensor is relatively constant. Images can be obtained withoutloss of optical quality.

Another dye that may be added to the non-fluid optical component is anelectrochromic compound. Herewith, the transparency can be set with ahelp of a voltage. This is allowable, as there is no other voltageapplied to the non-fluid optical component, except in the embodimentbelow. As the non-fluid optical component is in fact a pattern in thereplica layer, this pattern can be chosen to desire. Hence, ring-shapedstructures of varying height and negative lenses can be made. Suchstructures can be applied advantageously as diaphragms. Anotherpossibility is a structure that extends on the complete surface. Thiscan be used as a shutter.

In a preferred embodiment, the substrate including a first and a secondportion that are mutually connected through a expandable joint. Theexpandable joint is preferably a ring-shaped membrane with a non-planarsurface. The inclusion of such a membrane in the substrate can besuitably combined with the provision of moulded surface layers on theglass. In fact, the moulded surface layer can be provided on thesubstrate before the membrane and the provision of an aperture in thesubstrate at the location of the membrane. The use of such a expandablejoint is found to be very effective to cope with the volume expansion ofthe fluid as a function of the temperature, and to ensure a completefilling of the package.

Preferably, the non-fluid optical element is part of an encapsulationdefining the fluid chamber. However, in another embodiment, a furtherchamber is provided between the fluid focus optical element and thenon-fluid focus optical element. Such a chamber may contain lenses thatare provided on a substrate with replica technique. The replica layerwill then further contain a spacer that acts as a side wall of thechamber.

In again another embodiment the moulded surface layer comprises a liquidcrystalline material. Therewith a further variable focus optical elementis provided in the package. A single liquid crystalline optical elementwould introduce a dependence on the polarisation. This does not appearto be advantageous for lenses in camera modules, but is very interestingfor special applications such as that of optical recording. Liquidcrystalline elements can be stacked however, in which case there is achamber present. Liquid crystalline lenses are Fresnel lenses inparticular and known per se from U.S. Pat. No. 6,449,236. Liquidcrystalline lenses made with replica technique are described in thenon-prepublished patent application EP 04100449.0 (PHNL040107), which isincluded herein by reference.

In a preferred modification hereof, the liquid crystalline opticalelement acts as a lens and the fluid focus optical element acts as avariable diaphragm. The advantage of the application of the fluid focuselement as a diaphragm is that it can be tuned continuously. Theadvantage of the application of the liquid crystalline element as alens, in comparison to the reversed solution, is that the drivingvoltage of such a lens is substantially lower than that of a fluid focuslens.

It is preferred that the variable focus lens package comprises non-fluidoptical components at opposite sides of the fluid focus lens. At leastone of those optical components is a lens or has lens functionality bypreference.

It is furthermore preferred that alignment means for alignment withinthe variable focus package are present as well. Mechanical alignmentmeans are preferred, although optical alignment means can bealternatively used. The latter is particularly the case if the packageis assembled on a wafer-scale. Suitable examples of mechanical alignmentmeans include locking features, such as protrusions and correspondingcavities.

In another suitable embodiment, a moulded layer of a cross-linkedpolymer material with a lens function is present at an inner side of theencapsulation of the fluid chamber. It was found by the inventors thatcross-linking of the polymer improves the lifetime of the moulded layeragainst the fluids of the fluid focus lens. Particularly critical isherein the organic fluid, that is particularly a fluid of an apolar ornonpolar organic material.

The presence of a lens within the chamber is particularly advantage, inthat herewith the use of a separate grating structure can be dispensedwith.

These and other aspects of the invention will be further elucidated withreference to the figures, in which:

FIG. 1 is a diagrammatic cross-sectional view of the lens of theinvention;

FIG. 2 is an diagrammatic, exploded view of the lens.

FIG. 1 diagrammatically shows a variable focus lens package 2 accordingto a preferred embodiment of the present invention.

The variable focus lens package 2 comprises a plastic annular body 10,which is at least partially covered by a layer comprising electricallyconducting material, such as metal. The electrically conducting layer iscovered by a layer comprising an electrically insulating material, suchas parylene, whereas the electrically insulating layer is covered by alayer comprising a hydrophobic material. The three layers covering aportion of the body 10 are diagrammatically depicted in FIG. 1 by meansof a line, which is indicated by reference numeral 16.

The body 10 of the variable focus lens package 2comprises—bevelling—surfaces 13 which are located at an outer portion.Furthermore, at a bottom side, the body 10 is provided with an annulargroove 17.

A through-hole 11 of the body 10 is closed off by means of a bottom lensmember 30 which is located at the bottom side of the body 10 and a toplens member 70 which is located at the top side of the body 10. Bothlens members 30, 70 are formed as so-called replica lenses. Such lensescomprise a glass base plate 32, 74 and a plastic lens bodies 31 a. 31 b,75 a, 75 b, and are manufactured with a replica technique, with the useof a mould for moulding the plastic and UV-light for curing the plasticinside the mould, thus effecting cross-linking. Preferably thecross-linking density is at least 0.05 and preferably in the order of0.08-0.15. The outer lens bodies 31 b, 75 b comprise alignment means 33,76. These alignment means 33,76 are designed here to have an annularshape, but this is not necessary. In this example, the alignment meanshave the same height as the lens parts 75 b, 31 b, but that is by nomeans necessary; the moulding technique allows height variations asdesired.

The variable focus lens package 2 comprises a sealing ring 50 forsealing a fluid chamber 85 which is delimited by the body 10, a bottomsurface of the top lens member 70 and a top surface of the bottom lensmember 30. The sealing ring 50 is located between protruding annularportions 18, 19 of the body 10 and the base plate 74 of the top lensmember 70. The design of the lens may be amended so as to include morethan one sealing ring, if so desired.

According to an important aspect of the present invention, at both thetop surface 36 of the bottom lens member 30 and the bottom surface 76 ofthe top lens member 70, a positioning ring 38, 77 is arranged on thelens members 30, 70. The positioning rings 38, 77 play a role inaligning the lens members 30, 70 with respect to each other and withrespect to the through-hole 11 of the body 10. On the one hand, an outerdiameter of a bottom positioning ring 38 is chosen such that when thebottom lens member 30 is put in place with respect to the body 10, anouter circumference of the bottom positioning ring 38 contacts an outerwall 45 of the body 10, without the presence of play. In this way, acentral axis of the lens body 31 of the bottom lens member 30 is exactlyaligned with a central axis of the through-hole 11 of the body 10. Onthe other hand, an outer diameter of a top positioning ring 77 is chosensuch that when the top lens member 70 is put in place with respect tothe body 10, an outer circumference of the top positioning ring 77contacts the upright wall 46, without the presence of play. In this way,a central axis of the lens body 75 of the top lens member 70 is exactlyaligned with the central axis of the through-hole 11 of the body 10, andconsequently also with the central axis of the lens body 31 of thebottom lens member 30.

For the purpose of fixing the various lens package elements 10, 30, 50,60, 70, with respect to each other, clamping units can be used, whichare however not depicted. A clamping unit is for instance arranged suchas to clamp the top lens member 70 against the body 10, wherein thesealing ring 50 is clamped between the top lens member 70 and the body10.

The variable focus lens package 2 comprises a quantity of water 86 and aquantity of oil 87. The water 86 and the oil 87 are present in the fluidchamber 85, wherein the water 86 is situated at a bottom side of thefluid chamber 85, and wherein the oil 87 is situated at a top side ofthe fluid chamber 85. The water 86 and the oil 87 are separated by ameniscus 88. The shape of this meniscus 88 is variable under theinfluence of a voltage between the electrically conducting layer of thebody 10 and the water 86, as the wettability of the hydrophobic layerwith respect to the water is variable under the application of avoltage.

FIG. 2 diagrammatically shows an exploded view of a second embodiment ofthe variable focus lens package 2. The bottom lens member 30 comprises areplica lens having three layers. The replica lens comprises a glassbase plate 32, which is sandwiched between a plastic bottom lens layer31 a of which a central portion constitutes a concave lens body, and aplastic top lens layer 31 b of which a central portion constitutes aconvex lens body. Further, in the shown example, the top lens member 70also comprises a replica lens. This replica lens of the top lens member70 comprises a glass base plate 74 and a plastic top lens layer 75 ofwhich a central portion constitutes a convex lens body. It is observedthat the replica lenses 31 a, 31 b at opposing sides of the glass plate31 need not to have the same composition. A diacrylate layer is suitablefor the layer 31 a and a HDDA replica is suitable for the layer 31 b.The lenses are provided at the side of layer 31 b with coatings, such asanti-reflection coatings and UV-absorption coatings in a sputteringtreatment. Suitable anti-reflection coatings comprise titanium oxide ,silicon oxide and/or tantalum oxide.

An important feature of the lens package 2 is that the body 10 itselfmay be used as an electrical connector of the lens package 2, wherein itis not necessary that an additional element for contacting the body 10is applied. In order to avoid short-circuiting between the body 10 andthe layer 37 of the bottom lens member 30, a bottom surface 26 of thebody 10 is covered by an electrically insulating layer 27, at least atthe areas where the body 10 rests on the bottom lens member 30. Theshown body 10 is designed such as not to contact the top surface 36 ofthe bottom lens member 30 at an end of an inner portion 12 of the body10.

The body 10 may comprise clamping arms (not shown in FIG. 2) for fixingthe bottom lens member 30. However, it is also possible that clampingmeans for clamping the bottom lens member 30 against the body 10 areprovided, which are not formed as an integral part of the body 10. Thetop lens member 70 may be fixed with respect to the body 10 in anysuitable way, for example also by means of clamping means.

Besides the connector which is constituted by the body 10, the fourthvariable focus lens package 2 needs to comprise another connector (notshown in FIG. 2), which is in contact with the electrically conductinglayer 37 of the bottom lens member 30, in order to be in contact withthe water through this layer 37. This connector may be shaped andarranged in any suitable way, wherein it is important that the connectordoes not contact the body 10.

The variable focus lens packages 2 may be applied in hand-heldapparatus, such as mobile phones and optical scanning devices for use indigital recording equipment A number of lens packages 2 may bepositioned in a row, wherein the through-holes 11 of the lens packages 2are aligned with respect to each other, in order to create a zoom lens.Although the lens package 2 is shown to have lens parts at both sides ofthe glass plate 30, there is no need, and it is sufficient that theseare provided at the outside only. The lens packages 2 according to thepresent invention are particularly intended for application in a camera,which further comprises an image sensor and an interconnecting body,wherein the interconnecting body comprises electrically conductivetracks arranged on a first surface and a second surface of theinterconnecting body, and wherein the electrically conductive tracks areshaped such as to be able to establish a connection between both theimage sensor and the variable focus lens package 2 to driver electronicstherefore, or to contact pads. The camera may be part of theabove-mentioned hand-held apparatus, which may further comprise inputmeans, information processing means and display means.

1. Variable focus lens package (1, 2, 3) comprising a plurality ofoptical elements in a light path, which plurality of optical elementscomprises: a fluid optical element in a fluid chamber comprising a firstfluid (87) and a second fluid (86), which are non-miscible, and whichare in contact over a meniscus (88), wherein a shape of the meniscus(88) is variable under the application of a voltage to an electricallyconducting surface of the fluid chamber; a non-fluid optical component,of which fluid optical element and which non-fluid optical element atleast one is a lens, wherein the non-fluid optical component isconstructed from a substrate that comprises a transparent portion in thelight path, and from a moulded surface layer that is present at a sideof the substrate facing away from the fluid optical element and furthercomprises alignment means for alignment of the lens package with furtherlenses.
 2. A variable focus lens package as claimed in claim 1,characterized in that a second non-fluid optical component is present inthe light path in addition to the—first—non-fluid optical component,such that the fluid lens is sandwiched between the first and the secondnon-fluid optical component, which second non-fluid optical component isconstructed from a substrate that comprises a transparent portion in thelight path, and a moulded surface layer that is present at an outside ofthe encapsulation and further comprises alignment means for alignment ofthe lens package with further lenses.
 3. A variable focus lens packageas claimed in claim 1, wherein the substrate and a further carrierforming part of the encapsulation comprise alignment means for mutualalignment.
 4. A variable focus lens package as claimed in claim 1,wherein the alignment means comprise a ring-shaped protrusion or cavitycircumfering the light path.
 5. A variable focus lens package as claimedin claim 1, further comprising a moulded layer of a cross-linked polymermaterial with a lens function at an inner side of the encapsulation ofthe fluid chamber.
 6. A variable focus lens package as claimed in claim5, wherein said lens function at the inner side of the encapsulationfunctions as a grating.
 7. A variable focus lens package as claimed inclaim 1, wherein said non-fluid optical component is an aspheric lens.8. An assembly of a variable focus lens package according to claim 1 anda further lens, wherein the variable focus lens and the further lens arealigned to each other with the alignment means present in the mouldedsurface layer of the variable focus lens.
 9. A camera module comprisingan image sensor, a driver and a variable focus lens package according toclaim
 1. 10. An imaging apparatus provided with a variable focus lenspackage according to claim
 1. 11. A method of manufacturing a variablefocus lens package comprising a plurality of optical elements in a lightpath, which plurality of elements comprises: a fluid optical element ina fluid chamber comprising a first fluid (87) and a second fluid (86),which are non-miscible, and which are in contact over a meniscus (88),wherein a shape of the meniscus (88) is variable under the applicationof a voltage to an electrically conducting surface of the fluid chamber;a non-fluid optical element, of which fluid and non-fluid opticalelement at least one is a lens, in which method a plurality of suchpackages are made simultaneously with the steps of: assembling a carriercomprising a plurality of cavities filled with at least one of saidfluids to a substrate with transparent portions for each of the lightpaths, which substrate has a moulded surface layer that includes thenon-fluid lens and alignment means for alignment with further lenses,and separating said plurality of lenses into individual variable focuslenses packages.